Evaluation of fungicides for control of Sclerotinia drop of lettuce, Waynesville 2009.

摘要

The experiment was conducted at the Mountain Research Station in Waynesville, NC (N35deg29.344’; W082deg58.118’). Plots were bare ground double row beds on 42 in. centers, 20 ft long with 5-ft fallow borders at each end and non-treated guard rows oneach side. Lettuce was seeded in the greenhouse on 23 Mar and transplanted in the field on 29 Apr in double rows spaced 12 in. apart with 12 in. plant spacing within the row. Irrigation was applied via drip tape. Treatments were randomized into four complete blocks. On 12 May, plots were infested by spreading 100cc of S. sclerotiorum infested oat grain and incorporated into the top 1 in. of soil. Fungicide treatments were applied using a CO2-pressurized backpack sprayer equipped with a 2-nozzle (19 in.spacing), handheld boom with hollow cone nozzles (TXVS-26) delivering 40 gal/A at 45 psi. Applications were made on a 14-day interval: 13 and 26 May. Lettuce drop incidence was evaluated on 20 and 26 May, 4,10,17,24, and 30 Jun and 8 Jul. Disease incidence was assessed as the number of plants collapsed/diseased due to S. sclerotiorum. Average monthly high and low temperatures (Fdeg) for 2009 (1971-2000 year average) were 71/52 (73/46) in May, 81/57 (80/53) in Jun, and 78/58 (83/57) in Jul. Rainfall (in.) for 2009 (1971-2000 year average) was 8.17 (4.43) in May, 2.47 (4.03) in Jun, and 2.93 (3.59) in Jul.